But the prosecution expert said the pipes, which contained a potassium nitrate explosive mixture, could be readily assembled into a destructive device.

Special Agent Richard Stryker created replicas of the PVC pipes and their contents and tested them in a FBI laboratory. He used different percentages of a potassium nitrate mixture with varying amounts of Karo syrup and powdered sugar to generate a reaction.

"It would spin wildly out of control," Stryker said of the reaction when they were ignited with a safety fuse. "They wouldn't fly."

Some mixes produced a "forceful expulsion of smoke and gases," Stryker said. When he replaced the powdered sugar with Karo syrup, the pipes produced smoke or did nothing, he said. Other mixes produced little to no reaction.

Neither Stryker nor an FBI chemist who testified knows the ratio of potassium nitrate to sugar used in the PVC pipes recovered at Megahed's arrest.

Megahed, an Egyptian national, is accused of illegal transportation of explosive materials and a destructive device. He has denied knowing the PVC pipes were inside the trunk when he and Ahmed Mohamed, both University of South Florida students, were stopped for speeding in Goose Creek, S.C., on Aug. 4, 2007.

The defense has repeatedly referred to the materials as homemade sugar rockets or fireworks that were no more harmful than a road flare. Mohamed, an Egyptian student who had been in the United States for roughly six months before his arrest, became fascinated with fireworks after his first Fourth of July, his attorneys have said.

Mohamed said that he took the homemade fireworks along to visit beaches and celebrate his birthday with Megahed.

Stryker said no evidence was found indicating the men intended to use the pipes as model rockets, as defense attorneys have suggested.

"I don't know what the end use of this material is, per se," Stryker said on cross examination. "I don't know if it was intended to produce light, sound or heat."

Prosecutors have said they have no evidence about the students' intentions.

Nonetheless, Stryker testified that he took the materials recovered in the trunk, which included safety fuses and a partially filled gas can, and combined them to create an incendiary device. He wrapped the fuse around the gas can and used duct tape to secure the PVC pipe. It took five attempts to get the device to produce fire, the agent said.

Megahed's attorney, Adam Allen, said investigators didn't find duct tape in the car. Stryker said it was easily obtainable if the materials were to be converted into a destructive device.